The present invention relates to a network of central processing complexes (CPCs) connected by message paths to a structured external storage (SES) facility, each CPC having data objects used to maintain state information for shared data in the structured external storage facility, and more particularly relates to a mechanism in each CPC for verifying that a healthy path exists between the structured external storage facility and the CPC.
Commands executed by a structured external storage facility on behalf of one system image are designed to initiate signals to another system image in the same or a different CPC. The generated signals include cross-invalidates (XIs) and list-state transition notifications (LNs). Failure to successfully deliver a cross-invalidate signal has the potential to cause a data integrity exposure if the target system image erroneously considers data in a locally cached buffer to be current with respect to the version registered in the SES facility. Failure to deliver a list-state transition notification can result in a system hang if the initiative for interrogating the SES facility as a result of an empty to non-empty list state transitions is lost. Failure to successfully deliver and execute either type of signal can introduce sympathy sickness across all systems sharing the external storage facility if commands issued by these sharing system images are not allowed to execute successfully in order to avoid the aforementioned data integrity or system hang scenarios.